The inventive concept relates generally to semiconductor memory devices, and more particularly to a sense amplifier that senses and amplifies data of a semiconductor memory device.
Semiconductor memory devices can be roughly divided into two categories according to whether they retain stored data when disconnected from power. These categories include volatile memory devices, which lose stored data when disconnected from power, and nonvolatile memory devices, which retain stored data when disconnected from power. Examples of volatile memory devices include static random access memory (SRAM), dynamic RAM (DRAM), and synchronous DRAM (SDRAM). Examples of nonvolatile memory devices include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable and programmable ROM (EEPROM), NAND flash memory, NOR flash memory, phase-change RAM (PRAM), magnetic RAM (MRAM), resistive RAM (RRAM), and ferroelectric RAM (FRAM).
In a typical DRAM, a memory cell array is connected to a bitline BL and a complementary bitline BLB. In a read operation (or a refresh operation), a sense amplifier senses a voltage difference between a bitline BL and a complementary bitline BLB and amplifies the voltage difference.
The sense amplifier typically comprises various types of semiconductor devices, which can have different characteristics (e.g., threshold voltages) due to process variation and temperature. These different characteristics may generate offset noise in the sense amplifier. Additionally, coupling noise may occur due to coupling between bitlines. An effective sensing margin of the sense amplifier may be reduced due to the offset noise and the coupling noise, degrading performance of a DRAM device.